Specifications

MGX 8220 Service Modules 4-27
Frame Relay Access Service Module
An application of a BSTUN connection is shown in Figure4-13. An bisynch device, such as an
IBM 3270, is connected to a FRASM port using bisynch protocol. The traffic is first converted to
frame relay and then to ATM cells for transmission over the network. At the other end, the traffic is
first converted back to frame relay and the bisynch traffic is then extracted for transmission to a front
end communication processor and then to the IBM mainframe.
Figure4-13 Using FRASM for a BSTUN connection
Using BSTUN, the FRASM supports:
• Point-to-point bisynch lines.
• Multidropped bisynch devices over a single logical port. These can be assigned to different
connections.
• Multiple logical connections over a single logical port.
• Virtual multidrop in which bisynch devices attached to a FRAM on a different MGX 8220 shelf
can be configured to appear on multidropped devices on a single multidrop line.
FRAS Connections
FRAS BNN, short for Frame Relay Boundary Network Node, is a technique for encapsulating
SDLC/SNA traffic into frame relay frames (to RFC 1490) at one end of the connection only. At the
other end of the connection, the data is presented as frame relay. This is used for connecting an
SDLC device at one end to a frame relay device at the other.
SNA traffic received by the FRASM is converted first to a frame relay format and is then further
converted into cells for transmission over an ATM network, the ATM traffic is then converted back
to frame relay at the other end.
Using FRASM configured for FRAS BNN connections, many low speed SNA lines can be
consolidated into a smaller number of high speed lines for fast transport through the network. In
addition, FRAS BNN can be used for high speed links between IBM front end processors (FEPs).
FEPs running under Network Control Program (NCP) 7.1 support BNN.
An application of a FRAS BNN connection is shown in Figure4-14. An SDLC device is connected
to a FRASM port using SDLC protocol. The traffic is first converted to frame relay and then to ATM
cells for transmission over the network. At the other end, the traffic is first converted back to frame
relay for transmission to a front end communication processor and then to the IBM mainframe.